Secondary Battery Module

ABSTRACT

A secondary battery module includes a plurality of battery blocks each obtained by stacking a plurality of battery cells. The secondary battery module includes a holding member adapted to hold the plurality of battery blocks and including a pair of opposed end plates, a pair of opposed side plates, and a section plate arranged between the adjacent battery blocks to partition the battery blocks; and an inter-block bus bar provided across the section plate and adapted to electrically connect the adjacent battery blocks. The inter-block bus bar has a fuse portion.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Pat. Application No. 17/059,976, filed Nov. 30, 2020, which is a 371 of International Application No. PCT/JP2019/007086, filed Feb. 25, 2019, which claims priority to Japanese Patent Application No. 2018-118425, filed Jun. 22, 2018, the disclosures of all of which are expressly incorporated by reference herein.

BACKGROUND ART

Conventionally, a secondary battery module obtained by stacking a plurality of battery cells is known as a technique in such a field. In such a secondary battery module, the battery cells are electrically connected by bus bars. In addition, to prevent damage to the battery cells due to an abnormal overcurrent, a bus bar with a so-called fuse function is adopted by providing one of the plurality of bus bars with a fuse portion.

For example, Patent Literature 1 below discloses a secondary battery module having a bus bar with a fuse function that has a small cross-section portion (i.e., a fuse portion) with a cross-section smaller than those of the other portions. When an abnormal overcurrent flows through the bus bar, the fuse portion is allowed to fuse through generation of heat, thereby protecting the battery cells.

CITATION LIST Patent Literature

Patent Literature 1: JP 2013-73929 A

SUMMARY OF INVENTION Technical Problem

However, since the fuse portion of the aforementioned bus bar with a fuse function is formed thinner or narrower than the other portions, there has been a problem that when an external force, such as vibration or impact, is applied to the fuse portion, stress concentration is likely to occur in the fuse portion, which can break the fuse portion.

The present invention has been made to solve such a technical problem, and it is an object of the present invention to provide a secondary battery module in which stress applied to a fuse portion can be reduced and thus breakage of the fuse portion can be suppressed.

Solution to Problem

A secondary battery module according to the present invention is a secondary battery module with a plurality of battery blocks each obtained by stacking a plurality of battery cells, including a holding member adapted to hold the plurality of the battery blocks, the holding member including a pair of opposed end plates, a pair of opposed side plates, and a section plate arranged between the adjacent battery blocks to partition the battery blocks; and an inter-block bus bar provided across the section plate and adapted to electrically connect the adjacent battery blocks, in which the inter-block bus bar has a fuse portion.

In addition, a secondary battery module according to the present invention is a secondary battery module with at least one battery block obtained by stacking a plurality of battery cells, including a holding member adapted to hold the battery block, the holding member including a pair of opposed end plates and a pair of opposed side plates; and a plurality of bus bars at ends of the module, each of the plurality of bus bars at the ends of the module having one end electrically connected to the battery block and having another end extending toward one of the end plates or one of the side plates and electrically connected to an external connection terminal of the module, in which at least one of the plurality of bus bars at the ends of the module has a fuse portion.

Advantageous Effects of Invention

According to the present invention, stress applied to a fuse portion can be reduced, and thus breakage of the fuse portion can be suppressed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a secondary battery module according to a first embodiment.

FIG. 2 is a plan view of the secondary battery module according to the first embodiment.

FIG. 3 is a perspective view of a battery cell.

FIG. 4 is a perspective view of an inter-block bus bar.

FIG. 5 is a perspective view of a bus bar at an end of the module.

FIG. 6 is a schematic perspective view of battery blocks, which are held by a holding member, housed in a housing.

FIG. 7 is a plan view of a secondary battery module according to a second embodiment.

FIG. 8 is a plan view of a secondary battery module according to a third embodiment.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of a secondary battery module according to the present invention will be described with reference to the drawings. In the description of the drawings, identical elements are denoted by identical reference numerals, and overlapped descriptions will be omitted. In the following description, “the direction in which battery cells are stacked” may simply be referred to as “the stacked direction” to avoid complexity of description.

First Embodiment

FIG. 1 is a perspective view of a secondary battery module according to a first embodiment. FIG. 2 is a plan view of the secondary battery module according to the first embodiment. The secondary battery module 1 of the present embodiment mainly includes two battery blocks 10 each obtained by stacking a plurality of battery cells 11 in a given direction, and a holding member 20 adapted to hold the two battery blocks 10 arranged in series in the stacked direction of the battery cells 11.

Each battery block 10 is formed by stacking a plurality of (herein, 17) flat rectangular battery cells 11 in the stacked direction with interposed therebetween cell holders (not illustrated) each made of an insulating resin material.

FIG. 3 is a perspective view of each battery cell. As illustrated in FIG. 3 , the battery cell 11 includes a cell can 12 and a cell lid 13. The cell can 12 has a so-called closed-bottomed rectangular tube shape, and includes a rectangular can bottom portion 12 a; and a pair of opposed wide side face portions 12 b and a pair of opposed narrow side face portions 12 c arranged in upright position on the four sides of the can bottom portion 12 a, the pair of wide side face portions 12 b having relatively large areas, and the pair of narrow side face portions 12 c having relatively small areas. The cell can 12 houses a flat wound electrode group and an electrolytic solution, for example.

The cell lid 13 is approximately rectangular in shape, and is joined to the cell can 12 so as to cover the opening of the cell can 12. Examples of the joining method include laser welding. The cell lid 13 has a positive electrode terminal 14 and a negative electrode terminal 15 each provided in a protruding manner. Each of the positive electrode terminal 14 and the negative electrode terminal 15 has an end that is formed flat so as to be easily joined to an inter-cell bus bar 31, an inter-block bus bar 32, or a bus bar 33 at an end of the module (described below) by laser welding.

The cell lid 13 is provided with a gas exhaust valve 16. When the pressure in the battery cell 11 has increased, the gas exhaust valve 16 is opened to discharge the gas in the battery cell 11. Accordingly, the pressure in the battery cell 11 can be reduced, and thus the safety of the battery cell 11 can be secured. Further, the cell lid 13 is provided with a liquid inlet plug 17 for closing a liquid inlet for an electrolytic solution. The liquid inlet plug 17 is joined to the cell lid 13 by laser welding after the battery cell 11 is filled with an electrolytic solution via the liquid inlet, for example.

The plurality of battery cells 11 each having the aforementioned structure are stacked while being alternately inverted by 180° such that the positive electrode terminal 14 of one of the mutually adjacent battery cells 11 is adjacent to the negative electrode terminal 15 of the other battery cell 11. In addition, the positive electrode terminal 14 of one of the mutually adjacent battery cells 11 is electrically connected to the negative electrode terminal 15 of the other battery cell 11 by an inter-cell bus bar 31. The inter-cell bus bar 31 is formed flat using an aluminum material, for example, and is joined to the positive electrode terminal 14 and the negative electrode terminal 15 by laser welding while being placed on the positive electrode terminal 14 and the negative electrode terminal 15 so as to cover them.

The holding member 20 is formed in the shape of a box having an open upper face, for example, and includes a rectangular bottom plate portion 24; a pair of end plates 21 and a pair of side plates 22 arranged in upright position on the four sides of the bottom plate portion 24; and a section plate 23 disposed in a space formed by the bottom plate portion 24, the end plates 21, and the side plates 22.

The pair of end plates 21 are arranged on the opposite sides of the battery cells 11 in the stacked direction so as to face each other. Each end plate 21 is formed with a metallic material, for example, extends in a direction orthogonal to the stacked direction of the battery cells 11, and has a predetermined width in the stacked direction. Each end plate 21 has two screw holes 21 a with a predetermined distance therebetween. The end plates 21 are fastened to a housing 40 together with the bottom plate portion 24 using screws 25 inserted through the screw holes 21 a (see FIG. 6 ). The screws 25 are fastening members for fastening the end plates 21 to the housing 40 as described below.

The pair of side plates 22 are formed thinner than the end plates 21, and extend along the stacked direction. The side plates 22 are formed integrally with the bottom plate portion 24 by, for example, bending a single metal plate in a squared U-shape. It should be noted that the side plates 22 may also be formed separately from the bottom plate portion 24 and then fixed thereto by welding or with screws, for example.

Meanwhile, the section plate 23 is disposed between the battery blocks 10 so as to partition them, and is provided in parallel with the end plates 21. The section plate 23 is cuboid in shape, and has a relatively narrow portion along the stacked direction of the battery cells 11. Therefore, as illustrated in FIGS. 1 and 2 , the upper surface of the section plate 23 is a narrow face 23 a arranged along the stacked direction.

The section plate 23 has two screw holes 23 b with a predetermined distance therebetween. The section plate 23 is fastened to the housing 40 together with the bottom plate portion 24 using screws 25 inserted through the screw holes 23 b (see FIG. 6 ). The screws 25 are fastening members for fastening the section plate 23 to the housing 40 as described below.

The secondary battery module 1 of present embodiment further includes, in addition to the aforementioned inter-cell bus bars 31, an inter-block bus bar 32 adapted to electrically connect the adjacent battery blocks 10, and bus bars 33 at opposite ends of the module, each bus bar 33 at an end of the module being adapted to electrically connect the positive electrode terminal 14 or the negative electrode terminal 15 of one of the battery cells 11 of each battery block 10 to an external connection terminal 34 of the module arranged near each end plate 21.

The inter-block bus bar 32 is provided across the section plate 23, and electrically connects the positive electrode terminal 14 of one of the mutually adjacent battery blocks 10 to the negative electrode terminal 15 of the other battery block 10.

FIG. 4 is a perspective view of the inter-block bus bar. As illustrated in FIG. 4 , the inter-block bus bar 32 has a cross-section in an approximately hat shape, and includes a flat joint portion 32 a adapted to be joined to one of the positive electrode terminal 14 or the negative electrode terminal 15 of one of the mutually adjacent battery blocks 10, a flat joint portion 32 b adapted to be joined to the other of the positive electrode terminal 14 or the negative electrode terminal 15 of the other battery block 10, and a protruding portion 32 c arranged between the joint portions 32 a and 32 b and protruding outward from the battery cells 11. The center of the protruding portion 32 c is provided with a fuse portion 32 d that is formed narrower than the other portions of the inter-block bus bar 32. That is, the inter-block bus bar 32 is a bus bar with a fuse function. It should be noted that the fuse portion 32 d is arranged in the center of the protruding portion 32 c so as to face the narrow face 23 a of the section plate 23.

The inter-block bus bar 32 with such a structure is formed by, for example, machining a part of a single aluminum plate into a narrow shape at a place where the fuse portion 32 d is to be formed, and bending the plate into a hat shape. It should be noted that the inter-block bus bar 32 may also be formed using a clad material obtained by joining the protruding portion 32 c made of aluminum to the joint portions 32 a and 32 b each made of copper.

Meanwhile, each bus bar 33 at an end of the module has a plate shape, and one end of the bus bar 33 is electrically connected to the positive electrode terminal 14 or the negative electrode terminal 15 of the battery cell 11 that is most adjacent to one of the end plates 21, while the other end of the bus bar 33 extends toward the end plate 21 and is electrically connected to the external connection terminal 34 of the module.

FIG. 5 is a perspective view of each bus bar at an end of the module. As illustrated in FIG. 5 , each bus bar 33 at an end of the module is formed by, for example, bending a single aluminum plate into an approximately Z-shape, and includes a joint portion 33 a adapted to be joined to the positive electrode terminal 14 or the negative electrode terminal 15 of the battery cell 11 that is most adjacent to one of the end plates 21 and arranged at a relatively high level, an extension portion 33 b arranged at a relatively low level and extending toward the end plate 21, and a step portion 33 c arranged between the joint portion 33 a and the extension portion 33 b. The tip end of the extension portion 33 b is provided with a screw hole 33 d. The aforementioned external connection terminal 34 of the module is screwed into the screw hole 33 d and thus is fixed to the bus bar 33 at the end of the module.

Each bus bar 33 at an end of the module is fixed to one of the battery cells 11 as the joint portion 33 a of the bus bar 33 is welded to the positive electrode terminal 14 or the negative electrode terminal 15 of the battery cell 11. Though not illustrated, in a state in which the bus bar 33 at the end of the module is fixed to the battery cell 11, the bottom face of the extension portion 33 b of the bus bar 33 is away from the upper face of the end plate 21 and thus is electrically insulated from the end plate 21. Similarly, the bottom face of the external connection terminal 34 of the module screwed into the screw hole 33 d of the bus bar 33 at the end of the module is away from the upper face of the end plate 21 and thus is electrically insulated from the end plate 21.

The bus bar 33 at an end of the module with such a structure is provided on each of the opposite sides of the secondary battery module 1 in the stacked direction. That is, one of the bus bars 33 is adapted to electrically connect the positive electrode terminal 14 of the battery cell 11 located at one end in the stacked direction to one external connection terminal 34 of the module, and the other bus bar 33 is adapted to electrically connect the negative electrode terminal 15 of the battery cell 11 located at the other end in the stacked direction to the other external connection terminal 34 of the module. In addition, the external connection terminal 34 of the module, which is electrically connected to the positive electrode terminal 14 of the battery cell 11 via the bus bar 33 at one end of the module, functions as a positive electrode of the external connection terminal of the secondary battery module 1. Meanwhile, the external connection terminal 34 of the module, which is electrically connected to the negative electrode terminal 15 of the battery cell 11 via the bus bar 33 at an end of the module, functions as a negative electrode of the external connection terminal of the secondary battery module 1.

In the secondary battery module 1 according to the present embodiment, the inter-block bus bar 32 is provided across the section plate 23, and the inter-block bus bar 32 is provided with the fuse portion 32 d. The section plate 23 partially forms the holding member 20 and is a portion with a relatively high strength in the secondary battery module 1. As the inter-block bus bar 32, which has the fuse portion 32 d, is provided near the section plate 23 with a relatively high strength, stress applied to the fuse portion 32 d can be reduced, and thus breakage of the fuse portion 32 d due to external forces, such as vibration or impact, can be suppressed.

In addition, since the fuse portion 32 d is provided in the inter-block bus bar 32 so as to face the narrow face 23 a of the section plate 23, stress applied to the fuse portion 32 d can be reduced, and in comparison with when the fuse portion 32 d is provided facing the wide face (that is, a face extending in the longitudinal direction) of the section plate 23, for example, the protruding portion 32 c of the inter-block bus bar 32 can be made shorter. Consequently, the material used for the inter-block bus bar 32 can be reduced, and a cost reduction can thus be achieved.

Herein, when a housing adapted to house the battery blocks 10, which are held by the holding member 20, is provided, a fastening member for fastening the section plate 23 to the housing is preferably disposed near the fuse portion 32 d. Specifically, as illustrated in FIG. 6 , for example, the secondary battery module 1 further includes a housing 40 adapted to house the battery blocks 10 held by the holding member 20. The housing 40 is in the shape of a box, and houses two battery blocks 10 held by the holding member 20. Although FIG. 6 illustrates the housing 40 without a cover, the housing 40 may include a cover.

As illustrated in FIG. 6 , a bottom portion 41 of the housing 40 is provided with screw holes 41 a corresponding to the screw holes 21 a of the end plates 21 and the screw holes 23 b of the section plate 23. The inner wall of each screw hole 21 a has an inside screw formed therein. The battery blocks 10 held by the holding member 20 are fastened to the housing 40 with the screws 25 that have been inserted through the screw holes 21 a and 23 b and further through the screw holes 41 a.

At this time, the screws 25 for fastening the section plate 23 to the housing 40 are disposed near the fuse portion 32 d. Accordingly, the effect of reducing the stress applied to the fuse portion 32 d can be further increased. Thus, breakage of the fuse portion 32 d due to external forces, such as vibration or impact, can be suppressed.

Although the present embodiment has described an example in which the fuse portion 32 d is formed narrower than the other portions of the inter-block bus bar 32, the fuse portion 32 d may have the same width as the other portions of the inter-block bus bar 32 and be formed thinner than the other portions of the inter-block bus bar 32. Alternatively, the fuse portion 32 d may be formed narrower and thinner than the other portions of the inter-block bus bar 32. In this manner, changing the configuration of the fuse portion 32 d as appropriate can increase the versatility of the fuse portion 32 d and save materials more easily.

Second Embodiment

FIG. 7 is a plan view of a secondary battery module according to a second embodiment. A secondary battery module 1A of the present embodiment differs from the secondary battery module of the aforementioned first embodiment in that one of the two bus bars 33 at opposite ends of the module is a bus bar with a fuse function. The other structures are similar to those of the first embodiment. Thus, overlapped descriptions will be omitted.

As illustrated in FIG. 7 , the inter-block bus bar 32 is not provided with the fuse portion 32 d. Meanwhile, one of the two bus bars 33 at opposite ends of the module (i.e., the bus bar 33A at an end of the module on the right side in FIG. 7 ) is provided with a fuse portion 33 e. The fuse portion 33 e is formed between the screw hole 33 d of the extension portion 33 b and the step portion 33 c, and is narrower than the other portions of the bus bar 33A at the end of the module. The bus bar 33A at the end of the module is formed by, for example, machining a part of a single aluminum plate into a narrow shape at a place where the fuse portion 33 e is to be formed and forming the screw hole 33 d, and then bending the plate into a Z-shape.

According to the secondary battery module 1A of the present embodiment, operational advantages similar to those of the aforementioned first embodiment can be obtained. That is, the end plates 21 partially form the holding member 20 and are portions with a relatively high strength in the secondary battery module 1. When the bus bar 33A at an end of the module, which has the fuse portion 33 e, is provided near one of the end plates 21 with a relatively high strength, stress applied to the fuse portion 33 e can be reduced, and thus breakage of the fuse portion 33 e due to external forces, such as vibration or impact, can be suppressed.

In addition, in the present embodiment, a screw 25 for fastening the end plate 21 to the housing 40 is preferably disposed near the fuse portion 33 e. Accordingly, the effect of reducing the stress applied to the fuse portion 33 e can be further increased.

Although the present embodiment has described an example in which one of the two bus bars 33 at opposite ends of the module is a bus bar with a fuse function, both the two bus bars 33 at the opposite ends of the module may be bus bars each having a fuse function as appropriate, or alternatively, one of the two bus bars 33 at the opposite ends of the module may be a bus bar with a fuse function, and further, the inter-block bus bar 32 may also be a bus bar with a fuse function.

Third Embodiment

FIG. 8 is a plan view of a secondary battery module according to a third embodiment. A secondary battery module 1B of the present embodiment differs from the aforementioned second embodiment in having only one battery block 10. The other structures are similar to those of the second embodiment. Thus, overlapped descriptions will be omitted.

As illustrated in FIG. 8 , the secondary battery module 1B includes one battery block 10 and a holding member 20A adapted to hold the battery block 10. Therefore, the holding member 20A does not include the section plate 23 described in the first and second embodiments. In addition, one of the two bus bars 33 at opposite ends of the module (the bus bar 33A at an end of the module on the right side in FIG. 8 ) is provided with the fuse portion 33 e.

According to the secondary battery module 1B of the present embodiment, operational advantages similar to those of the second embodiment can be obtained.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited thereto, and various designs changes can be made without departing from the spirit and scope of the present invention recited in the claims. For example, although the second and third embodiments have described examples in which the bus bars 33 at opposite ends of the module extend toward the end plates 21, the bus bars 33 at the opposite ends of the module may extend toward the side plates 22. In such a case, one of the external connection terminals 34 of the module may be fixed to the extension portion, which extends toward one of the side plates 22, of one of the bus bars 33 at the opposite ends of the module.

Reference Signs List 1, 1A, 1B Secondary battery module 10 Battery block 11 Battery cell 20, 20A Holding member 21 End plate 21 a Screw hole 22 Side plate 23 Section plate 23 a Narrow face 23 b Screw hole 25 Bottom plate portion 25 Screw (fastening member) 31 Inter-cell bus bar 32 Inter-block bus bar 32 a, 32 b, 33 a Joint portion 32 c Protruding portion 32 d, 33 e Fuse portion 33, 33A Bus bar at end of module 33 b Extension portion 33 c Step portion 33 d Screw hole 34 External connection terminal of module 40 Housing 

1. A secondary battery module with a plurality of battery blocks each obtained by stacking a plurality of battery cells, the secondary battery module comprising: a pair of end plates arranged on both sides of the battery blocks in a stacking direction of the battery cells and facing each other, a pair of side plates facing each other, and a section plate disposed between the battery blocks to partition the battery blocks; and an inter-block bus bar provided across the section plate and adapted to electrically connect the adjacent battery blocks; wherein the inter-block bus bar is provided with a fuse portion which is narrower and/or thinner than other portions of the inter-block bus bar.
 2. The secondary battery module according to claim 1, wherein the section plate has a narrow face arranged along a stacked direction of the battery cells; and the fuse portion of the inter-block bus bar is provided so as to face the narrow face of the section plate.
 3. The secondary battery module according to claim 1, further comprising a housing that accommodates the plurality of battery blocks, wherein the section plate has a fastening hole in which a fastening member to be fastened with the housing is accommodated.
 4. The secondary battery module according to claim 1, further comprising a housing that accommodates the battery blocks, wherein the end plate has a fastening hole in which a fastening member to be fastened with the housing is accommodated.
 5. The secondary battery module according to claim 1, wherein the inter-block bus bar has a joint portion that is joined to the battery blocks, the joint portion is made of copper, and the fuse portion is made of aluminum.
 6. A secondary battery module having a battery block in which a plurality of battery cells are stacked, the secondary battery module comprising: a pair of end plates arranged on both sides of the battery block in the stacking direction of the battery cells and facing each other, and a pair of side plates facing each other; and a plurality of module end bus bars, a first end of which is electrically connected to the battery block and a second end of which extends toward the end plate or the side plate and is electrically connected to an external connection terminal of the secondary battery module; wherein at least one module end bus bar of the plurality of module end bus bars is provided with a fuse portion formed narrower and/or thinner than other portions of the at least one module end bus bar. 